WO2017203446A1

WO2017203446A1 - Method for the manual preparation of concrete by means of mechanical suspension

Info

Publication number: WO2017203446A1
Application number: PCT/IB2017/053062
Authority: WO
Inventors: Carlos Mauricio BEDOYA MONTOYA
Original assignee: Universidad Nacional De Colombia
Priority date: 2016-05-25
Filing date: 2017-05-24
Publication date: 2017-11-30

Abstract

The invention relates to a method for the production of concrete mixtures and mortar mixtures. The method comprises the following steps: a) mixing and agitating a cementing agent with water until an activated paste is produced; b) adding a fine aggregate to the activated paste from step (a) and agitating until a mortar mixture is produced; and c) adding a coarse aggregate to the mixture resulting from step (b), and agitating until a concrete mixture is produced. In addition, the invention comprises an activated paste, a mortar mixture and a concrete mixture.

Description

CONCRETE MANUAL CONFECTION PROCEDURE THROUGH

Field of the Invention

The present invention relates to concrete mixtures, mortar mixtures and the process for obtaining them, specifying the order and times in which each mixing component must be added, and the resulting product.

Description of the technical state

Conventional concrete mixtures (hereinafter MCV) consists of three essential elements: cement, water, and aggregates that can be thin and / or thick.

The MCVs are carried out in an MVC preparation process (hereinafter MCV process), adding the components in the following order: 1) mix and stir the cement and aggregates until a substantially homogeneous mixture is obtained; Y,

2) add water to the composition obtained in step (1), and mix and stir until a substantially homogeneous mixture is obtained. A substantially homogeneous mixture is understood as a mixture that in essence or in a portion greater than 50% of its composition comprises a single phase.

After the MCV is performed, it is arranged in molds that describe a volume that depends on the user's requirements. After depositing the MCV in molds, it enters a process that is called hardened, in which for 28 days it must gradually reach properties and values of compressive strength that are between the ranges of 21 to 25MPa according to the NTC 550 standards of the Icontec, equivalent to ASTM C31. In the state of the art the patent document GB 1053958 A is identified which discloses a method of making mixtures of mortars and concrete, for improve mechanical resistance to compression. Conventional materials are used in this method: water, cement and fine and coarse aggregates.

The steps comprising the GB1053958A patent method are:

ground the cement particles in the presence of water while undergoing a partial vacuum; Y,

b- add the fine and / or coarse aggregates. These can be added during crushing or after the wet cement particles have been crushed.

Given the previous disclosures, a process is required for the reaiízación of mixture of concrete and mortars that in the same proposal:

enhance the activation capacity of the cementing agent: and,

b- increase compressive strength and durability.

Brief description of the invention

The present invention corresponds to a process for the preparation of concrete and mortar mixtures, in a mixing process with mechanical suspension (hereinafter the MSM process).

The MSM process comprises the stages of:

a- mix and stir a cement with water until an activated paste is achieved;

b- add a fine aggregate to the activated paste of step (a) and stir until a substantially homogeneous composition is achieved, in a plastic state; Y,

c- add a coarse aggregate to the mortar mixture obtained in step (b), and stir until a concrete mixture with a substantially homogeneous composition is achieved.

The invention also comprises the products obtained with the MSM process. The products are an activated paste, a mortar mixture and a concrete mixture.

The activated paste comprises water and a cement. The cement and water are stirred and mixed until a substantially homogeneous composition is achieved. The mortar mixture comprises an activated paste and a fine aggregate. The activated pass and the fine aggregate are stirred and mixed until a substantially homogeneous composition is achieved in the plastic state.

The concrete mixture comprises a mortar mixture and a coarse aggregate. The mortar mixture and coarse aggregate are stirred and mixed until a substantially homogeneous composition is achieved. Brief description of the figures.

FIG. 1 shows a 1000X electronic scanning microscopy performed on the MCV sample prepared using a ¡V1CV process. In the figure you can see the porosity areas.

The FiG. 2 shows a 1000X electronic scanning microscopy performed on the MSM sample made using an MSM process. In the figure you can see the porosity areas. Detailed description of the invention

The present invention corresponds to a process for the preparation of concrete and mortar mixtures, in a mixing process with mechanical suspension (hereinafter the MSM process). The invention also comprises Sos products obtained with the MSM process.

The MSM process comprises the following stages:

a- mix and stir a cement with water until an activated paste is achieved;

c- add a coarse aggregate to the mortar mixture obtained in step (b), and stir until a concrete mixture with a substantially homogeneous composition is achieved. In step (a), stirring is performed manually. For this, water and cement are placed in a tank, where they are agitated. Step (a) is carried out until a homogeneous substantial composition is obtained, which is called activated pulp. To achieve activated pulp, stirring is carried out in a time T1, where 0 <T1≤ 2 min.

In step (b), the activated paste of step (a) and the fine aggregate are mixed and stirred until a substantially homogeneous composition is achieved in a plastic state, which is called mortar mixture. To achieve the mortar mixture, stirring is carried out in a time T2, where 0 <T2≤ 4 min.

In stage (c), the mortar mixture from stage (b) and the coarse aggregate are mixed and stirred until a substantially homogeneous composition is achieved, which is called concrete mixing. To achieve concrete mixing, stirring is carried out in a time T3, where 0 <T3≤ 4 min.

Within the scope of the present invention, cementing will be understood as compounds that bind fragments of one or more substances and give permanent cohesion to such a set. The union occurs through chemical transformations, which arise from the contact of the cement with water. Therefore, the cementing agent is selected from the group consisting of Portland type I cements (known in Colombia as general purpose cement), Portland type II, Portland type III, Portland type IV, lime, gypsum, ashes, binders and combinations of previous.

Within the scope of the present invention, the plastic state will be understood as the phase where the concrete or mortar mixture acquires properties that allow it, despite its low fluidity, to adequately fill forms or deposits according to the user's requirements.

The ratio of the materials for the mixture of water, cement and aggregates (fine aggregate and coarse aggregate) is established by the user according to the requested mixing requirements. In one embodiment of the invention, the ratio of materials for the mixture of water, cement and aggregates is between 1: 2: 2.5 and 1: 2: 3 respectively.

Example 1 A cubic meter of concrete has been developed using the MSM process. The elements used are:

- water: 181, 89 kg (L)

- Cementing: Portland cement type I: 394.40 kg

- fine aggregate: 788.8 kg

- coarse aggregate: 986.0 kg

For the elaboration of concrete the following stages were executed:

a) mix and stir portland cement type I with water for a while

T1 = 2 min until the activated paste is achieved:

b) add a fine aggregate to the activated pulp of step (a) and stir for a time T2 = 4 min until the substantially homogeneous composition is achieved, in the plastic state; Y,

c) add a coarse aggregate to the mortar mixture obtained in step (b), and stir for a time T3 = 4 min until a concrete mixture with a substantially homogeneous composition is achieved.

To the concrete elaborated with the MSM process you were tested for "severity determination". The "severity determination" test is defined in ASTM C642: Standard Test Method for Density, Absorption, and Voids IN Hardened Concrete, whose equivalent standard in Colombia is NTC 5853. For the "determination" test of gravity "two samples were extracted, the four were titled as MSM 1 and MSM 2.

Additionally, in order to compare the results of this test with those of a concrete made by means of an MCV process, a concrete was elaborated through said process. The same amounts of water, Portland cement type I and aggregates were used for concrete made by MCV. Two samples were extracted from the concrete made by MCV, which were titled MCV 1 and MCV 2.

The results of the "severity determination" test on samples MCV 1, MCV 2, MSM 1 and MSM 2 are indicated in Table 1.

According to Sa norm, for the preparation of mixtures it is desirable to obtain as a result of the test absorption percentages and void percentages with low values. The lower the percentage absorption value, it is an indication that during the hardening process, the mixture assumed extra low amounts of liquids. This means that the amounts of the components used to make the mixture were adequate, and in its hardening process it did not require additions or external agents to properly complete its hardening.

With respect to the percentage values of voids, it is a condition that falls on the structural properties. A mixture that obtains in its hardening process low percentages of voids, indicates that it has in its structure less porosity. This means that there is a greater number of cohesion channels between fine and coarse aggregates, which allows for higher load transfer capabilities (it has greater compressive strength).

According to the above, the MSM 1 and MSM 2 samples have lower absorption and lower pore volume compared to the MCV 1 and MCV 2 samples. That is, the MSM 1 and MSM 2 samples have higher performance values in terms of durability. concrete to atmospheric agents as dissolved CO ₂ in air. CO ₂ is the cause of carbonation, a pathology that rapidly degrades the life of the reinforced concrete structures.

When making a comparison between average values of absorption percentage between the MCV 1 and MCV 2 samples, and MSM1 and MSM 2 of Table 1, a difference of 0.45% absorption can be seen; since the average of the MCV 1 and MCV 2 samples in the absorption value is 10%, while in the MSM 1 and MSM 2 samples is 9.55%. According to the norm, the last value is more desirable than the first.

Likewise, in comparing the average values of the percentage of voids between the MCV 1 and MCV 2 samples, and MSM1 and MSM 2 in Table 1, a difference of 0.70% of voids can be seen; since the average of fas samples MCV 1 and MCV 2 in the absorption value is 21, 85%, and that of samples MSM 1 and MSM 2 is 20.95%. In accordance with the standard, the last value is more desirable than the first, for the preparation of mixtures.

Additionally, the individuals were tested for the "Blaíne" property. The "Blaine" property is a property of the cementing agent, which indicates the coating capacity in square centimeters per gram (cm ² / g), which is measured by optimizing the consumption of the cementing agent and guaranteeing a mixture of greater cohesion for the fine aggregates and thick. The "Blaíne" Sa property test can be performed by scanning electron microscopy (SEM) tests. By scanning electron microscopy, areas of porosity and lack of "Blaíne" coating are identified. For the realization of the "Blaine" property test, samples of the concrete were extracted. The sample of the concrete produced by the MSM process was titled MSM and the sample of the concrete prepared by the MCV process was titled MCV.

Referring to FIG. 1, the scanning microscopy of the MCV sample performed at 10.00X shows regions with porosity and lack of "Blaine" which are delimited with black ovals that enclose numbers (1), (2) and (3).

Referring to FIG. 2, in scanning microscopy of the MSM sample performed at 1000X, regions with porosity and lack of "Blaine" are evidenced, which are delimited with black ovals that enclose the number (4).

When comparing the microscopes of FIG 1 and FIG 2, it is notable that the regions with porosity and lack of "Blaine" in the MSM sample are less and smaller than in the MCV sample. The foregoing indicates that the cementing agent had a higher coating capacity in MSM compared to MCV. Likewise, it is indicated that there is greater cohesion for fine aggregates and coarse aggregates.

Claims

1. A process for the preparation of concrete mixtures and mortar mixtures comprising the following stages:

a) mix and stir a cement with water until an activated paste is achieved;

b) add a fine aggregate to the activated paste of step (a) and stir until a mortar mixture is achieved; Y

c) add a coarse aggregate to the mixture resulting from step (b), and stir until a concrete mixture is achieved;

where the ratio between water, cement and aggregates is between 1: 2: 2.5 and 1: 2: 3, respectively.

2. The process of Claim 1, characterized in that in step (a) the stirring is carried out in an IT time less than or equal to 2 min.

3. The process of Claim 1, characterized in that in step (b) the stirring is carried out in a time T2 less than or equal to 4 min.

4. The process of Claim 1, characterized in that in step (c) the stirring is carried out in a time T3 less than or equal to 4min.

5. The process of Claim 1 characterized in that the cement is selected from the group consisting of: Portland type I, Portland type II, Portland type III, Portland type IV, lime, gypsum, ashes and combinations of the above.

6. An activated paste comprising:

-Water; Y,

-a cement;

wherein the cement and water are stirred and mixed until a substantially homogeneous composition is achieved.

7. A mortar mixture comprising:

an activated paste, and

a fine aggregate;

wherein the activated paste and the fine aggregate are stirred and mixed until a substantially homogeneous composition is achieved in a plastic state.

8. A concrete mixture comprising:

a mixture of mortar; Y,

a thick aggregate;

wherein the mortar mixture and coarse aggregate are stirred and mixed until a substantially homogeneous composition is achieved.